7 of the World’s Deadliest Plants

They may look harmless enough, but plants can harbor some of the most deadly poisons known. From the death of Socrates by poison hemlock to the accidental ingestion of deadly nightshade by children, poisonous plants have been responsible for human deaths throughout history. Get to know some of the most infamous plants and their poisons with this macabre list.

7Water Hemlock (Cicuta maculata)

Closely related to poison hemlock (the plant that famously killed Socrates), water hemlock has been deemed "the most violently toxic plant in North America." A large wildflower in the carrot family, water hemlock resembles Queen Anne's lace and is sometimes confused with edible parsnips or celery. However, water hemlock is infused with deadly cicutoxin, especially in its roots, and will rapidly generate potentially fatal symptoms in anyone unlucky enough to eat it. Painful convulsions, abdominal cramps, nausea, and death are common, and those who survive are often afflicted with amnesia or lasting tremors.

6Deadly Nightshade (Atropa belladonna)

belladonnacredit: J. Fujishima/B.W. Halstead, World Life Research Institute

According to legend, Macbeth’s soldiers poisoned the invading Danes with wine made from the sweet fruit of deadly nightshade. Indeed, it is the sweetness of the berries that often lures children and unwitting adults to consume this lethal plant. A native of wooded or waste areas in central and southern Eurasia, deadly nightshade has dull green leaves and shiny black berries about the size of cherries. Nightshade contains atropine and scopolamine in its stems, leaves, berries, and roots, and causes paralysis in the involuntary muscles of the body, including the heart. Even physical contact with the leaves may cause skin irritation.

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5White Snakeroot (Ageratina altissima)

white snakerootcredit: Sten Porse

An innocuous plant, white snakeroot was responsible for the death of Abraham Lincoln's mother, Nancy Hanks. White snakeroot is a North American herb with flat-topped clusters of small white flowers and contains a toxic alcohol known as trematol. Unlike those who have died from directly ingesting deadly plants, poor Nancy Hanks was poisoned by simply drinking the milk of a cow who had grazed on the plant. Indeed, both the meat and milk from poisoned livestock can pass the toxin to human consumers. Symptoms of "milk poisoning" include loss of appetite, nausea, weakness, abdominal discomfort, reddened tongue, abnormal acidity of the blood, and death. Luckily farmers are now aware of this life-threatening hazard and make efforts remove the plant from animal pastures.

4Castor Bean (Ricinus communis)

castor-oil plantcredit: J. Fujishima/B.W. Halstead, World Life Research Institute

Widely grown as an ornamental, the castor bean is an attractive plant native to Africa. While the processed seeds are the source of castor oil, they naturally contain the poison ricin and are deadly in small amounts. It only takes one or two seeds to kill a child and up to eight to kill an adult. Ricin works by inhibiting the synthesis of proteins within cells and can cause severe vomiting, diarrhea, seizures, and even death. The poison was used in 1978 to assassinate Georgi Markov, a journalist who spoke out against the Bulgarian government, and has been mailed to several U.S. politicians in failed terrorism attempts. Most fatalities are the result of accidental ingestion by children and pets.

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3Rosary Pea (Abrus precatorius)

jequirity beancredit: Luon Kwan-Ming Li/B.W. Halstead, World Life Research Institute

Also called jequirity beans, these piously-named seeds contain abrin, an extremely deadly ribosome-inhibiting protein. Rosary peas are native to tropical areas and are often used in jewelry and prayer rosaries. While the seeds are not poisonous if intact, seeds that are scratched, broken, or chewed can be lethal. It only takes 3 micrograms of abrin to kill an adult, less than the amount of poison in one seed, and it is said that numerous jewelry makers have been made ill or died after accidentally pricking their fingers while working with the seeds. Like ricin, abrin prevents protein synthesis within cells and can cause organ failure within four days.

2Oleander (Nerium oleander)

common oleandercredit: Joaquim Alves Gaspar

Described by Pliny the Elder in Ancient Rome, oleander is a beautiful plant known for its striking flowers. Though commonly grown as a hedge and ornamental, all parts of the oleander plant are deadly and contain lethal cardiac glycosides known as oleandrin and neriine. If eaten, oleander can cause vomiting, diarrhea, erratic pulse, seizures, coma, and death, and contact with the leaves and sap is known to be a skin irritant to some people. Indeed, the toxins in oleander are so strong that people have become ill after eating honey made by bees that visited the flowers! Fortunately, fatalities from oleander poisoning are rare, as the plant is very bitter and thus quickly deters anyone sampling the vegetation.

1Tobacco (Nicotiana tabacum)

Tobacco is the most widely grown commercial non-food plant in the world. All parts of the plant, especially its leaves, contain the toxic alkaloids nicotine and anabasine, and can be fatal if eaten. Despite its designation as a cardiac poison, nicotine from tobacco is widely consumed around the world and is both psychoactive and addictive. Tobacco use causes more than 5 million deaths per year, making it perhaps the most deadly plant in the world.